According to a recent forecast, at the end of 2014, a quantity of wireless mobile devices will exceed a quantity of human beings for the first time, and at the end of 2018, a quantity of mobile devices per person in the world will reach 1.4. Data traffic of mobile services in 2018 will probably reach approximately 10 times that in 2013.
In the mobile Internet application field, various future applications such as augmented reality, virtual reality, or real-time interactive games will enhance user experience to a higher level. This imposes a higher requirement on a rate of a transmission network. On the other hand, emergence of mobile education, mobile health, and driverless cars will impose a greater challenge on a delay and reliability of future wireless communication. As new applications of wireless communication emerge continuously and become increasingly important, the transmission network certainly also needs to provide effective support through continuous evolution.
To better meet development requirements of mobile Internet services, a fifth-generation mobile communications technology (5G for short) network is becoming a hot topic of research of a current wireless communications network. 5G is a wireless communications system oriented to years after 2020. Therefore, with respect to 5G design requirements, a more challenging target needs to be defined to support development requirements of mobile services after 2020. Currently, with respect to 5G service requirements and target design, a data traffic target is designed according to 1000 times the current data traffic. With respect to a quantity of terminal devices that can be supported, a challenging target is to support 100 times the current quantity of terminal devices. In addition, it is required that a typical data rate of a terminal should also approach a target of 100 times. In addition to such a high performance challenge, a zero delay or a very low delay in comparison with an existing delay is further required, so as to meet requirements of some special services.
In a word, performance of 5G is far higher than that of a fourth-generation mobile communications technology (4G for short). 5G supports a user-perceived rate of 0.1 Gbps to 1 Gbps, and has a quantity of one million connections per square kilometer in density, an end-to-end delay in milliseconds, a traffic density with tens of Tbps per square kilometer, mobility higher than 500 km per hour, and a peak rate of tens of Gbps. In addition, deployment and operation efficiency of the 5G-era network is enhanced significantly, spectral efficiency is enhanced by 5 to 15 times against 4G, and energy efficiency and cost efficiency are enhanced by more than 100 times. To meet design requirements in the foregoing aspects, small cells or small-cell base stations are deployed more densely, forming a so-called ultra dense network (UDN for short).
In the UDN network, to provide a rate supported by the network, a large quantity of small-cell base stations are deployed. As more small-cell base stations are deployed in the network, cell changes occur frequently when user equipment (User Equipment, UE for short) moves in the dense network. However, each cell change process may relate to signaling interaction processes between the UE and an evolved NodeB (eUTRAN NodeB, eNB for short), between the UE and a core network device (such as an MME and an S-GW), and between the eNB and the core network device. With increase of cell change processes, a quantity of related signaling also increases. Especially, when an intelligent terminal supports more services, with introduction and use of various new services, frequent service setup and release processes of various services are also caused, and each service setup and release process also causes signaling to increase. On the other hand, due to introduction of a large quantity of machine type devices, for example, increase of a quantity of intelligent cars and other machine type devices, the network needs to frequently transmit a large quantity of small data packets. To transmit a small data packet every time, a service setup and release process needs to be performed. This also causes signaling load to increase, and therefore, a large quantity of resources are consumed every time a small data packet is transmitted.
Some ultra high frequency (UHF for short) bands (for example, a 700 MHz frequency band) that are originally used for broadcast and television services are allocated to a mobile operator, and the premium spectrum resources featuring wide coverage have revolutionary impact on mobile communication. Therefore, when some UHF frequency bands or other lower frequency bands are allocated to a mobile service, how to use these spectrum resources properly and bring features of the spectrum resources into full play is also a very critical problem.
In a conventional Long Term Evolution (LTE for short) technology, every time UE accesses a network, an eNB first needs to set up a radio resource control (RRC for short) connection, and then set up a non-access stratum (NAS for short) connection to a mobility management entity (MME for short) and a serving gateway (S-GW for short). When the network needs to transmit a service to the UE, first, the MME delivers a paging notification to a base station in a paging area or a tracking area, and then the base station in the paging area or the tracking area sends a paging message to the UE. In the foregoing small cell network, and especially in a scenario of dense deployment, a macro network covers a large quantity of small cells. When the UE moves at a medium or high moving speed, serving cells change frequently, and every cell change process relates to a cell measurement, cell measurement result reporting, and a cell handover command. In addition, a cell handover process further relates to signaling interaction processes between the eNB and a network element of the core network such as the MME or the S-GW.
In the processes of setting up and releasing various future services, the UE sets up and releases network connections frequently, and the UE spends a long time in accessing the network every time. As the cell network is deployed more densely, cell changes occur more frequently, and consequently, signaling related to the cell changes increases abruptly.
In addition, as a large quantity of small-cell base stations are deployed in the network, a quantity of base stations in a paging area is very large. Complying with a conventional paging mechanism, that is, delivering a paging message on all base stations in the paging area, also causes paging signaling to increase abruptly, and therefore, costs of the small-cell base stations also increase due to increase of paging load. In addition, the delay in the conventional LTE technology is long. For example, every time the UE accesses the network, it takes 80 ms+2T_S1. T_S1 is generally in a range of 20 ms to 100 ms, and therefore, a delay of the UE is approximately 100 ms to 180 ms.